Means for performing an extrusion process in a cold forging press



May 26, 1970 E. MONESTAM MEANS FOR PERFORMING AN EXTRUS ION PROCESS IN A COLD FORGING PRESS Filed Oct. 13, 1967 INVENTOR. ES IL AACSNESTAM United States Patent O 3,513,681 MEANS FOR PERFORMING AN EXTRUSION PROCESS IN A COLD FORGING PRESS Eskil Monestam, Robertsfors, Sweden, assignor to Allmanna Svenska Elektriska Aktiebolaget, Vasteras, Sweden, a corporation of Sweden Filed Oct. 13, 1967, Ser. No. 675,086 Claims priority, application Sweden, Oct. 13, 1966, 13,867/ 66 Int. Cl. B21c 27/00 US. Cl. 72272 1 Claim ABSTRACT OF THE DISCLOSURE An extrusion matrix with external conicity clamped with strong pre-stressing in a conical pressure cylinder, the matrix being releasable under influence of an expelling force acting on the forging.

BACKGROUND OF THE INVENTION Field of the invention The prior art When cold forging in a forging press, it is extremely important to prevent the forging from sticking to adjacent surfaces of the tool, and for this reason the substance is supplied with a lubricating layer by means of a relatively complicated surface treatment. During extrusion the lubricating layer is subjected to considerable wear which can easily mean that the lubrication is insuflicient during expulsion and the work piece is damaged.

SUMMARY OF THE INVENTION The above-mentioned disadvantage is avoided with a device according to the invention which is based on the principle of eliminating the pressure of the matrix against the object during expulsion.

A device according to the invention is characterised in that said conicity is achieved narrowing in the pressing.

direction and that the matrix within a certain range is movable under the influence of the expelling force transmitted from the forging to the matrix.

With a device according to the invention the special difficulties are also eliminated which arise when the ob ject produced during extrusion is so long that there is a danger of its snapping or being deformed during expulsion.

3,513,681 Patented May 26, 1970 lCC BRIEF DESCRIPTION OF THE DRAWING The invention will be described in the following with reference to the accompanying drawing where FIG. 1 and FIG. 2 show the device in longitudinal section, FIG. 1 showing the device in the final stage of forging and FIG. 2 during expulsion of the forging.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The matrix 1 is externally conical and fits into an annular body 2 which is pre-stressed in the pressure cylinder 3 of the tool. During forging the matrix will be pressed down until it stops against a ring 4 above the pressureequalising plate 5 and is thus, due with the external cone, compressed to suitable radial pre-stressing. This is chosen so that when the matrix during expulsion moves upwards out of the cone, the radial expansion of the matrix will be sufliciently great for its grip on the extruded detail to cease. Thus in this way the pressure of the matrix on the final object is eliminated as desired. The matrix 1 is prevented from rising too high during expulsion since a stop on this matrix stops against the ring 4 which is manu factured in parts to enable it to be mounted. The system may also be designed so that the lining 6 of the moulding space is also provided with sloping surfaces so that the pre-stressing of the lining ceases when it is moved upwardly. In this way even the unextruded part of the forging 7 can be pushed out under such conditions that no pressure, or only moderate pressure, is exerted against the wall of the moulding space.

I claim:

1. Means for performing extmsions in a cold forging press, said means comprising means forming a pressure chamber, and a matrix with external conicity arranged at the bottom of said pressure chamber, the pressure chamber forming means including an annular body into which said matrix can enter, said annular body having strong prestressing and being shaped with an internal conicity corresponding to the external conicity of the matrix, said matrix decreasing in cross-section in the pressing direction, and said pressure chamber forming means and said matrix having cooperating projection and recess means for allowing limited movement of the matrix within a certain range with respect to the pressure chamber forming means under the influence of an expelling force transmitted from forging to the matrix.

References Cited UNITED STATES PATENTS 1,379,717 5/1921 Parsons et a1. 72467 2,389,876 11/ 1945 Sequin 72272 2,860,775 11/1958 Brauchler 72272 LOWELL A. LARSON, Primary Examiner US. Cl. X.R. 72-467 

